Psyche Probe on Its Way to Asteroid Belt

Image credit: NASA/JPL-Caltech/ASU/Peter Rubin

Powered by a Hall thruster producing "250 millinewtons of force — about the amount of force that you would feel from the weight of holding one AA battery." 

Newton's first law of motion states that an object continues in its state of rest or uniform motion in a straight line, unless acted on by an external force. So once you give something a push in space, it keeps going. That doesn't happen on Earth because the external force in this case is drag, due to friction from the air. That slows an object down. Newton's second law of motion basically says that acceleration is proportional to force, so while the quarter-newton propulsion force is small and provides little acceleration, velocity increases over time. So unlike conventional rocket propulsion which generates high acceleration for a short period of time, Hall thrusters gently accelerate spacecraft for periods of months or years, to slowly build up velocity.

You can read more about the Psyche mission in this article on the NASA website. 

New Home and Garden Website

© Eugene Brennan

You might like my new website, Home and Garden Guidebook. It features comprehensive and practical guides, with tips and advice for home improvement, gardening, DIY and everyday projects.

The Abolition of the Leap Second

AI image created using Bing Image Creator

You may have heard Dr Shane Bergin speaking about this on Today with David McCullagh this morning. Leap seconds are being abolished and replaced by a system that will eventually allow a leap hour to be added, although that is unlikely to happen for thousands of years.

Leap seconds were introduced because a day isn't exactly 86,400 seconds long. Billions of years ago, a day was only about five hours long. According to a research article published in the academic journal Paleoceanography and Paleoclimatology, a day lasted approximately 23.5 hours during the Cretaceous Period, around 70 million years ago.

The gravitational interaction between the Earth and the Moon produces tidal effects that gradually slow the Earth's rotation. Leap seconds were added at irregular intervals to keep the time shown on our clocks closely aligned with the Earth's rotation and, consequently, the apparent motion of the Sun across the sky.

The last leap second was added on 31 December 2016, at 23:59:60 UTC. It was the 27th leap second added since 1972. The adjustments can cause problems for computer systems and other digital infrastructure, so international timekeepers have now agreed to phase them out in favour of a system that allows a much larger difference between atomic time and time based on the Earth's rotation.

In contrast, we will still need leap years because the Earth takes approximately 365.25 days to orbit the Sun, rather than exactly 365 days. Adding an extra day to February in leap years keeps our calendar aligned with the seasons. Without this adjustment, the dates of the seasons would gradually drift through the calendar, and Christmas would eventually fall in summer.

 

You can read more about the changes here on Scientific American. 

Scientists just voted to redefine how the world keeps time 

Solar Lighting for Dark Spots in the Town

Solar powered lighting
 Image created by Grok

I'm looking at the datasheets for these Philips SunStay streetlamps, which could be an option for lighting up dark areas in the town. One advantage is that an ESB Networks connection wouldn't be necessary, reducing installation costs. However, the luminaires can also be powered by mains electricity if desired. I haven't looked at the price, though. The entry-level model has the following specs:

•     2000 lumen output, 28/35 W solar panel

•     11 W LED output (with an efficiency of 175 lm/W)

•     PIR sensor with a 5 metre range

•     The streetlamps operate at 30% output throughout the night, ramping up to 100% when a pedestrian is detected

•     A "ClearField" amber-red light recipe can be factory-configured for the LED module, producing a shorter-wavelength, lower colour temperature, amber-red output, making lights less disruptive to bats (see link below). However, efficiency is lower and typically 70 lm/W. I.e, lights appear dimmer

Solar irradiance is worst in December, with a worst-case scenario of 1 peak sun hour (PSH) per day in the north of the country to 2 PSH in the south, according to Met Éireann. For a 35 W panel, that's a potential storage of 35 watt-hours (Wh) of energy. When the 2000 lumen model is operating at 30% output, consumption is 30% x 11W = 3.3 Wh per hour. So a lamp wouldn't quite last a full night on a solar charge, but probably up to 10.5 hours.
Might be useful for the Valley park, the walkway between the AFC and GAA pitches, the Sunny Hill road from Cnoc na Gréine to the Newbridge Road etc.
Maybe worth trialling one?

Signify was formerly Philips Lighting, but became a spinoff and independent company in 2016.

This is the 2000 lumen model:

SunStay — All in one solar street light

 
Bat-friendly options:

A lighting solution — minimizing the night-time disturbance of bats

Met Éireann sunshine information:

Sunshine and Solar Radiation

ESB Report on Rainfall Management

Water level in the Poulaphouca Reservoir. Graph courtesy ESB.

Water level in the Poulaphouca Reservoir is now at 183.68 mOD, roughly midway between the upper and lower operating levels of 186.30 mOD and 179.90 mOD respectively. According to the Wicklow County Council-commissioned Blessington eGreenway Flood Risk Assessment document, 

"The flood period operation begins when the conditions require spilling of excessive flood waters until normal operating conditions are re-established. This flood period operation occurs when the Poulaphouca Reservoir level is greater than 186.30mOD Poolbeg (183.6mOD Malin)"

Water level is well below this and has plateaued over the last 6 days, with water inflow equal to water outflow. This July report from the ESB details how the lake acted as a buffer and managed heavy rain during the early part of 2026. Without the lake to moderate flow, huge amounts of flooding in towns downstream would be possible. 

Graph courtesy ESB website. 

Beam Steering in the LHC: New Magnets Reach Full Power

View of the LHC tunnel sector 3-4
Maximilien Brice (CERN), CERN Document Server, Attribution-Share Alike 3.0 Unported

Within the 8.5 km-diameter Large Hadron Collider (LHC), sub-atomic particles are accelerated to close to the speed of light by electric fields in radiofrequency (RF) cavities.

Teeth Are Harder Than Steel

Hardness of various materials
Infographic created by Grok

Did you know that on a modified Mohs hardness scale that runs from 1 to 10, tooth enamel would rank at 5? That's harder than mild steel at 4.0 to 4.5 and softer than glass at 5.5.

Reduction in Rate of Water Level Decrease in Poulaphouca

Water level in the Poulaphouca Reservoir
Image courtesy ESB

The water level in the Poulaphouca Reservoir is still dropping, albeit at a slower weekly average than a month ago, when it was falling by about 2 cm to 2.5 cm per day.

Printer Frustration and Vodafone Broadband Goes Down

I resorted to dismantling my printer during the outage. Didn't have any success with that. Three blank cartridges — one filled with Quink ink (which worked successfully for over a year) and a brand new one wouldn't work.

Hard-to-Read Maps: Issues With Google Maps and OpenStreetMap

Tailte Éireann map

Whenever I'm out and about, it's nearly impossible to make out L roads on maps on my phone in bright sunlight because of the low contrast.

"Flood" on the River?

Flow versus time for Golden Falls dam
Image courtesy ESB hydro

Does anyone know whether the ESB are generating from the Golden Falls power station? Forecasted flow has been 3 m³/s for the last week or two. However actual flow is tabulated at 2 m³/s.

How Fast Is the Level Dropping in the Poulaphouca Reservoir?

Poulaphouca lakeside
© Eugene Brennan 

A question was asked on the Blessington Blog today to the effect, “Will the lake get as low as this again over the next weeks?” It showed a photo of the Poulaphouca Reservoir taken during a previous drought, in which neat linear piles of rocks could be seen along the shoreline, clearly marking the locations of the walls of houses that were submerged when the valley was flooded in the 1940s.

What Are Clicks?

Image made by Grok.

What's the difference between a click or thump sound (e.g. when you hit something with a stick or hammer a nail) compared to striking a bell or a string in a musical instrument? It's mainly due to the amount of damping involved.

How To View What's Behind Your Washer Drum

© Eugene Brennan

You can check what's between the inner and outer drums of a washing machine, or check for limescale build-up on the heating element, by spinning the drum and illuminating it with a bright torch.

Three Reasons the Summer is Warmer Than the Winter

Created with ChatGPT.

A common misconception is that the Earth is closer to the Sun in summer, but it's actually further away. Diagrams would be better for explaining this. I'll get around to it, but I'll try to do it with words for now. 

What Are Voltage Regulators Used For?

78XX series of voltage regulators. E.g. 7805 and 7812 having regulated outputs of plus 5 volts and plus 12 volts respectively. Silverxxx, CC BY SA 3.0 Unported via Wikimedia Commons.

We're surrounded by electronic gadgets and appliances, and even devices that don't appear to be electronic may use electronic circuitry internally. For electronics to work properly, it's imperative that voltage be stable and constant.

How to Measure Length, Distance and Area on Google Maps

Public domain image from Canva

The Google Maps measuring tool can be used to measure the distance between two points, and the result is displayed in feet and metres. Alternatively, values are displayed in miles and kilometres if a user zooms out to view a greater-sized region of the map.

Resistors in Series and Parallel: Formula Derivation and Examples

© Eugene Brennan

Formulas for Resistors in Series and Parallel

Resistors are ubiquitous components in electronic circuitry both in industrial and domestic consumer products. Often, in circuit analysis, we need to work out the values when two or more resistors are combined. In this tutorial, we'll work out the formulas for resistors connected in series and parallel.

The Cork-Dublin Transmission Pipeline and Gas Distribution to Kilcullen

Gas distribution network in central Kilcullen from the interactive Dial Before You Dig website. Image courtesy Gas Networks Ireland.

On 4th March last year, a press release was issued by Uisce Éireann to media and local public representatives to the effect that:

“Civil Engineers are carrying out pre-work activities on the 225mm pipeline, which involves a localised crossing over the High Transmisison (sic) Gas main under the supervision of Gas Networks.”

Immersion Heaters and Potential Fire Risks

Immersion heater terminal box. (AI enhanced as the original photo was blurry)
© Eugene Brennan

So I was doing some gardening for the sister today and she mentioned a smell that was coming from her immersion. This immediately rang alarm bells in my engineering head, knowing what was likely to have happened—So I investigated.